WO2019242434A1

WO2019242434A1 - Vacuum cleaner, and back electromotive force zero crossing detection method and apparatus and control system for motor

Info

Publication number: WO2019242434A1
Application number: PCT/CN2019/087066
Authority: WO
Inventors: 王浩东; 吴偏偏
Original assignee: 江苏美的清洁电器股份有限公司; 美的集团股份有限公司
Priority date: 2018-06-19
Filing date: 2019-05-15
Publication date: 2019-12-26

Abstract

Disclosed in the present application are a vacuum cleaner, and a back electromotive force zero crossing detection method and apparatus and a control system for a brushless direct current motor. The method comprises: obtaining a back electromotive force zero crossing detection time slot of a brushless direct current motor; and detecting and confirming the entry into the back electromotive force zero crossing detection time slot, continuously sampling the back electromotive force of the brushless direct current motor multiple times, and performing zero crossing detection on the back electromotive force according to the sampling result. The method can not only accurately detect a back electromotive force zero crossing point in time, but also ensure the motor to stably operate at extremely high rotation speed. Moreover, it is unnecessary to add an additional comparator, and the costs can thus be reduced.

Description

Zero-crossing detection method, device and control system of vacuum cleaner and motor

Cross-reference to related applications

This application is based on a Chinese patent application with application numbers of 201810628717.9 and 201810628718.3, the filing date of which is June 19, 2018, and claims the priority of the Chinese patent application. The entire contents of the Chinese patent application are incorporated herein by reference.

Technical field

The present application relates to the technical field of motor control, and in particular, to a method for detecting a back-EMF zero-crossing of a brushless DC motor, a device for detecting a back-EMF zero-crossing of a brushless DC motor, a control system for a brushless DC motor, and a vacuum cleaner.

Background technique

At present, in the technical field of sensorless drive control of a brushless DC motor, there are various methods for detecting the rotor position of a motor, among which the back-EMF zero-crossing method is simple, effective, and widely used. The basic principle of the back-EMF zero-crossing method is that when the back-EMF of a phase winding of a brushless DC motor crosses zero, the direct axis of the rotor coincides with the winding axis of that phase, so as long as the back-EMF zero-crossing point of each phase winding can be determined, Know the rotor position of the motor.

In the related technology, there are two methods for detecting the back-EMF zero crossing: First, the ADC (Analog-to-Digital Converter) module is used to sample at each PWM (Pulse Width Modulation) control cycle. The terminal voltage of the floating phase of the brushless DC motor is compared once, and then the sampling result is compared with the reference voltage to determine whether a zero crossing has occurred. Second, an external comparator is added to compare the terminal voltage of the floating phase of the brushless DC motor with the reference voltage by using hardware. Relationship to achieve back-EMF zero-crossing detection.

However, the above detection method has the following disadvantages: 1) When the method 1 is used to perform back-EMF zero-crossing detection, the detected back-EMF zero-crossing time lags behind the actual back-EMF zero-crossing time is about one PWM cycle, and in a brushless DC motor When the rotation speed of the PWM control signal is low, there are multiple PWM cycles in one commutation interval, and the lag of one PWM cycle has less effect on the commutation of the brushless DC motor. However, when the rotation speed of the brushless DC motor is small, When it is higher, the number of PWM cycles in one commutation interval is less. The back-EMF zero-crossing detection lag may lead to the brushless DC motor commutation lag, which affects the stability of the brushless DC motor. 2) Use method 2 When performing back-EMF zero-crossing detection, the cost will be higher due to the addition of an external comparator.

Summary of the Invention

This application is intended to solve at least one of the technical problems in the related technology. For this reason, the first purpose of this application is to propose a back-EMF zero-crossing detection method for a brushless DC motor, which can not only detect the back-EMF zero-crossing point in a timely and accurate manner, ensure stable operation of the motor at extremely high speeds, but also eliminate the need for Adding extra comparators can reduce costs.

A second object of the present application is to propose a non-transitory computer-readable storage medium.

A third object of the present application is to provide a back-EMF zero-crossing detection device for a brushless DC motor.

A fourth object of the present application is to provide a control system for a brushless DC motor.

A fifth object of the present application is to propose a vacuum cleaner.

In order to achieve the above objective, an embodiment of the first aspect of the present application proposes a method for detecting a back-EMF zero-crossing of a brushless DC motor, including the following steps: obtaining a back-EMF zero-crossing detection time gap of the brushless DC motor; detecting and It is confirmed that the back-EMF zero-crossing detection time gap is entered, the back-EMF of the brushless DC motor is continuously sampled multiple times, and the back-EMF is detected according to the sampling result.

According to the back-EMF zero-crossing detection method of the brushless DC motor according to the embodiment of the present application, the back-EMF zero-crossing detection time gap of the brushless DC motor is obtained, and the back-EMF zero-crossing detection time gap is detected and confirmed. The back-EMF of the brushless DC motor is continuously sampled multiple times, and the back-EMF is zero-crossed according to the sampling result. Therefore, not only the back-EMF zero-crossing point can be detected in a timely and accurate manner, and the motor can be stably operated at a very high speed, but also without an additional comparator, which can reduce costs.

In order to achieve the above object, an embodiment of the second aspect of the present application proposes a non-transitory computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above-mentioned back-EMF of the brushless DC motor is implemented. Zero detection method.

According to the non-transitory computer-readable storage medium of the embodiment of the present application, by performing the above-mentioned method of detecting the back-EMF zero-crossing of the brushless DC motor, the back-EMF zero-crossing can be detected in a timely and accurate manner, and the stable operation of the motor at the pole High speed and no need for additional comparators can reduce costs.

In order to achieve the above object, a back-EMF zero-crossing detection device for a brushless DC motor provided in an embodiment of the third aspect of the present application includes: an obtaining unit, configured to obtain a back-EMF zero-crossing detection time gap of the brushless DC motor A confirming unit configured to detect and confirm entering the back-EMF zero-crossing detection time gap; a sampling unit configured to continuously and repeatedly sample the back-EMF of the brushless DC motor according to a confirmation result of the confirming unit, and Zero-crossing detection is performed on the back-EMF according to a sampling result.

According to the back-EMF zero-crossing detection device of the brushless DC motor according to the embodiment of the present application, the back-EMF zero-crossing detection time gap of the brushless DC motor is acquired by the acquisition unit, and the back-EMF zero-crossing detection is detected and confirmed by the confirmation unit. Time gap, and the sampling unit performs multiple consecutive samplings of the back EMF of the brushless DC motor according to the confirmation result of the confirmation unit, and performs zero crossing detection on the back EMF according to the sampling result. Therefore, not only the back-EMF zero-crossing point can be detected in a timely and accurate manner, and the motor can be stably operated at a very high speed, but also without an additional comparator, which can reduce costs.

In order to achieve the above object, an embodiment of the fourth aspect of the present application proposes a control system of a brushless DC motor, which includes the above-mentioned back-EMF zero crossing detection device of the brushless DC motor.

According to the control system of the brushless DC motor in the embodiment of the present application, the above-mentioned back-EMF zero-crossing detection device of the brushless DC motor can not only detect the back-EMF zero-crossing point in a timely and accurate manner, and ensure that the motor runs stably at a very high speed. And without the need for additional comparators, it can reduce costs.

In order to achieve the above object, an embodiment of the fifth aspect of the present application provides a vacuum cleaner including the above-mentioned control system of a brushless DC motor.

According to the vacuum cleaner of the embodiment of the present application, through the above-mentioned control system of the brushless DC motor, not only the back-EMF zero-crossing point can be detected in a timely and accurate manner, the stable operation of the motor at extremely high speed can be ensured, but no additional comparator is needed, which can reduce the cost.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a flowchart of a method for detecting a back-EMF zero-crossing of a brushless DC motor according to an embodiment of the present application;

FIG. 2a is a terminal voltage waveform diagram of a period of phase A;

FIG. 2b is a terminal voltage waveform diagram of a phase A suspension period; FIG.

3 is a schematic diagram of a back-EMF zero-crossing detection of a brushless DC motor in the related art;

4 is a schematic diagram of a back-EMF detection time gap according to an embodiment of the present application;

5 is a schematic diagram of a back-EMF detection time gap according to another embodiment of the present application;

6a-6b are schematic diagrams of back-EMF zero-crossing detection of a brushless DC motor according to an embodiment of the present application;

7a-7c are flowcharts of a method for detecting a back-EMF zero-crossing of a brushless DC motor according to a specific embodiment of the present application;

FIG. 8 is a schematic diagram of a back-EMF zero-crossing detection of a brushless DC motor according to an embodiment of the present application; FIG.

FIG. 9 is a schematic block diagram of a back-EMF zero-crossing detection device of a brushless DC motor according to an embodiment of the present application.

detailed description

Hereinafter, embodiments of the present application are described in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary, and are intended to explain the present application, and should not be construed as limiting the present application.

The following describes a method for detecting a back-EMF zero-crossing of a brushless DC motor, a non-transitory computer-readable storage medium, a device for detecting a back-EMF zero-crossing of a brushless DC motor, and a brushless DC motor according to embodiments of the present application with reference to the drawings. Control system and vacuum cleaner.

FIG. 1 is a flowchart of a method for detecting a back-EMF zero-crossing of a brushless DC motor according to an embodiment of the present application. As shown in FIG. 1, a method for detecting a back-EMF zero-crossing of a brushless DC motor according to an embodiment of the present application includes the following steps:

S1. Obtain the back-EMF zero-crossing detection time gap of the brushless DC motor.

S2. Determine whether the back-EMF zero-crossing detection time gap is entered. Among them, it is judged whether to enter the back-EMF zero-crossing detection time gap, that is, whether to enter the back-EMF zero-crossing detection stage.

S3. If the back-EMF zero-crossing detection time gap is entered, the back-EMF of the brushless DC motor is continuously sampled multiple times and it is determined whether the back-EMF crosses zero.

According to an embodiment of the present application, before the back-EMF zero-crossing detection time gap of the brushless DC motor is obtained, the duty ratio of the PWM control signal of the brushless DC motor may also be obtained, and whether the duty ratio is greater than the first preset Set the duty cycle. If the duty cycle is greater than the first preset duty cycle, obtain the back-EMF zero-crossing detection time gap of the brushless DC motor, and determine whether it enters the back-EMF zero-crossing detection time gap, and within the back-EMF zero-crossing detection time gap , The back-EMF of the brushless DC motor is sampled multiple times in succession, and it is judged whether the back-EMF crosses zero; if the duty cycle is less than the second preset duty cycle, the The back-EMF of the brushed DC motor is sampled once, and it is determined whether the back-EMF crosses zero according to the sampling result. Among them, the second preset duty cycle is smaller than the first preset duty cycle, which can be calibrated according to the actual situation.

Specifically, the current back-EMF zero-crossing detection is comparing the relationship between the voltage of the floating phase terminal and the reference voltage. Taking phase A as an example, the voltage waveform of the phase A winding during a period is shown in FIG. 2a, and during the period of BC and CB, the phase A is floating, and the waveform of the terminal voltage is shown in FIG. 2b. During the PWM ON period, the phase A terminal voltage U _A = e _A + 1 / 2U _DC . When U _A = 1 / 2U _DC , e _A = 0, which is the time when the opposite potential of A is zero. During the PWM off period, A-phase terminal voltage U _A = e _A , when U _A = 0, it is the time when the opposite potential of A is zero. Therefore, the back-EMF zero-crossing detection is performed during the PWM on-time, the reference voltage is selected as 1 / 2U _DC , and the back-EMF zero-crossing detection is performed during the PWM-off period, and the reference voltage is selected as 0V.

In the related art, when the ADC module is used to sample the terminal voltage of the floating phase once in each PWM control cycle, and the sampling result is compared with the reference voltage to determine whether the back-EMF crosses zero, the back-EMF is detected during PWM on-time. Take zero crossing as an example. As shown in Figures 2a and 2b, during the BC turn-on period, the phase A terminal voltage is increasing. During each PWM turn-on period, the phase A terminal voltage is sampled once and compared with the reference voltage. A1 in Figure 2b At time, U _A <1 / 2U _DC , the back EMF does not cross zero. At time a2 of the next PWM control cycle, U _A > 1 / 2U _DC , it is detected that the back EMF has passed zero. At the same time, the CB is turned on. During the period, the phase A terminal voltage showed a downward trend. At time b2, U _A > 1 / 2U _DC , the back EMF did not cross zero, and at time b3, U _A <1 / 2U _DC , at this time it was detected that the back EMF had passed zero .

The detected back-EMF zero-crossing time lags behind the actual back-EMF zero-crossing time by about one PWM control cycle. In the case of low speed (low duty cycle), there are multiple PWM control cycles in one commutation interval. Therefore, lagging one PWM control cycle has less effect on commutation. However, when the brushless DC motor runs at a very high speed, such as 100000RPM (1 pair of poles), the time of one phase sector is 100us, and one PWM control cycle is 50us (that is, 20KHz, the PWM of the brushless DC motor). The frequency of the control signal is generally in the range of 5 ~ 30KHz, and then increasing it will adversely affect the switching loss, efficiency, and heat dissipation of the power switch. At this time, there is a maximum of 2 PWM control cycles in a commutation interval, and each PWM The control cycle only performs one back-EMF zero-crossing sampling, so it is not possible to know in time whether the back-EMF zero-crossing occurs, and it is easy to cause the brushless DC motor to lose step due to the large back-EMF zero-crossing detection lag.

Specifically, as shown in Figure 3, when the brushless DC motor is running at a very high speed, there are only 2 PWM control cycles in a commutation interval. If the conventional back-EMF sampling method is used, the two PWM control cycles A back-EMD (Analog-to-Digital, analog-to-digital conversion) sampling is performed in each of them, corresponding to time c1 and c2 respectively, and the actual back-EMF zero crossing occurs after time c1, so it cannot be within the first PWM control cycle Back-EMF zero-crossing is detected in time. The back-EMF zero-crossing can only be detected at time c2 of the second PWM control cycle, and the real back-EMF zero-crossing point at time c2 is about 1 PWM control cycle (about 1/2 change Phase interval), resulting in the back-EMF zero-crossing detection lag, which in turn leads to commutation lag, causing bad conditions such as large current ripples and out of step.

Therefore, in the embodiment of the present application, the operation of the brushless DC motor can be divided into two phases, namely a low speed phase and a high speed phase. Further, according to the duty cycle of the PWM control signal, the brushless DC motor can be The operation is divided into a low duty cycle phase and a high duty cycle phase. Among them, in the low duty cycle stage (that is, the low-speed stage), the conventional back-EMF zero-crossing detection method is still used, for example, one back-EMF AD sampling is performed in each PWM control cycle, and the back-EMF is judged according to the sampling result. zero. When the duty cycle rises above the first preset duty cycle, it enters the high duty cycle stage (that is, the high-speed stage). In this stage, because there is a freewheeling process after the commutation of the brushless DC motor, During this freewheeling period, the voltage of the floating phase terminal is forcibly pulled to the bus voltage or power ground, causing some back-EMF waveforms to be obliterated. Therefore, it is invalid to perform back-EMF zero-crossing detection during free-wheeling. Immediate back-EMF zero-crossing detection may be affected by the switching tube, resulting in inaccurate back-EMF zero-crossing detection. Therefore, a variety of factors that may affect the accuracy and timeliness of back-EMF zero-crossing detection are comprehensively considered. After commutation of the brushless DC motor, the back-EMF of the brushless DC motor is entered when the back-EMF zero-crossing detection time gap is entered. Performing multiple consecutive samplings can save CPU resources. Therefore, in the high duty cycle stage, during each PWM control cycle, when the back-EMF zero-crossing detection time gap is entered, the back-EMF of the brushless DC motor is continuously Sampling multiple times and determine if the back EMF crosses zero. When the duty cycle drops below the second preset duty cycle again, the conventional back-EMF zero-crossing detection method is used again.

Since the back-EMF zero-crossing detection lag in the low duty cycle stage has almost no effect on the commutation of the brushless DC motor, the control requirements can be met by using the conventional back-EMF zero-crossing detection method in the low-speed operation stage of the brushless DC motor. During the high duty cycle phase, the back-EMF of the brushless DC motor can be sampled multiple times continuously during the back-EMF zero-crossing detection time interval, so the timeliness and accuracy of the back-EMF zero-crossing detection can be guaranteed, which can support brushless The DC motor runs stably in the extremely high speed range without additional comparators, which can reduce costs and reduce the size of the controller PCB.

It should be noted that in practical applications, the electric speed of the brushless DC motor can reach more than 80,000 r / min.

According to an embodiment of the present application, obtaining the back-EMF zero-crossing detection time gap of the brushless DC motor includes: obtaining the first N back-EMF zero-crossing interval times, wherein N is obtained according to the current rotation speed; and according to the previous N back-EMF passes Zero interval time to obtain the time corresponding to the half sector of the current speed; to obtain the back-EMF zero-crossing detection advance time of the brushless DC motor; to obtain the difference between the time corresponding to the half-sector and the back-EMF zero-crossing detection advance time To get back EMF zero crossing detection time gap.

According to an embodiment of the present application, the back-EMF zero-crossing detection method of the brushless DC motor further includes: judging whether the time corresponding to half a sector from the last commutation time to the current time and the back-EMF zero-crossing detection advance time are between If the difference between the time between the last commutation time and the current time exceeds half a sector and the back-EMF zero-crossing detection advance time, the back-EMF zero-crossing detection time gap is entered.

According to an embodiment of the present application, obtaining the time corresponding to the lower half of the current speed of the brushless DC motor includes: obtaining the number of sampling times of the back-EMF zero-crossing interval according to the current speed, and obtaining the number of previous samples The time interval of the second back-EMF zero crossing; according to the previous sampling times, the time of the second back-EMF zero-crossing interval to obtain the time corresponding to the lower half of the current rotation speed.

According to an embodiment of the present application, the time corresponding to the half sector of the current speed can be obtained by the following formula:

Among them, Ts0 is the time corresponding to the half sector at the current rotation speed, Tzci is the i-th back-EMF zero-crossing interval time, and N is an integer greater than or equal to 1.

According to an embodiment of the present application, obtaining the back-EMF zero-crossing detection advance time of the brushless DC motor includes: obtaining the back-EMF zero-crossing detection advance time according to the highest operating speed of the brushless DC motor; or, passing a look-up table according to the current speed Obtain the back-EMF zero-crossing detection advance time; or, based on the current rotation speed, obtain the back-EMF zero-crossing detection advance time through a look-up table and a linear interpolation algorithm.

Specifically, considering a variety of factors that may affect the accuracy and timeliness of back-EMF zero-crossing detection, the back-EMF zero-crossing detection time gap after brushless DC motor commutation can be obtained. When obtaining the back-EMF zero-crossing detection time interval, the first N back-EMF zero-crossing intervals (the time interval between the two back-EMF zero-crossings) can be obtained first, for example, the first N back-EMF zero-crossing intervals obtained For Tzc1, Tzc2, Tzc3, Tzc4, ..., TzcN, and then according to the obtained first N back-EMF zero-crossing interval times to obtain the time Ts0 corresponding to the half sector at the current speed (30 ° electrical angle corresponds to half sector), As shown in the following formula (2):

The value of N is related to the current speed of the brushless DC motor. In practical applications, N can be set in sections according to the speed of the motor. For example, the speed range of a brushless DC motor is w ₀ to w _x (x is an integer greater than or equal to 2). The speed range of a brushless DC motor can be divided into w ₀ to w ₁ , w ₁ to w ₂ , ..., w _x-1 to w _x total x intervals, when the speed of the brushless DC motor is in the range of w ₀ to w ₁ , the corresponding value of N is N1; when the speed of the brushless DC motor is w ₁ to w ₂ Within the range, the value corresponding to N is N ₂ ; ...; when the speed of the brushless DC motor is in the range of w _x-1 to w _x , the value corresponding to N is N _x .

It can be understood that if the brushless DC motor runs at a constant speed, after the commutation of the brushless DC motor, the time Ts0 corresponding to half a sector is exactly the time of the zero-crossing of the back EMF, but in actual operation, the brushless DC motor The speed of the motor fluctuates, the time of each sector is uneven, and when the load changes quickly, the time of the sector will also fluctuate. Therefore, in order to be able to detect the back-EMF zero-crossing point in a timely and reliable manner, the start time of the back-EMF zero-crossing detection needs to be slightly advanced, that is, a period before the expected back-EMF zero-crossing point (that is, the back-EMF zero-crossing detection advance time Ta). , The back-EMF zero-crossing detection is started.

The back-EMF zero-crossing detection advance time Ta of the brushless DC motor can be determined by the following three methods: 1) The back-EMF zero-crossing detection advance time Ta can be set to a fixed value, and the fixed value can be determined according to the brushless DC Configure the maximum operating speed of the motor; 2) Update the back-EMF zero-crossing detection advance time Ta in real time by checking the table according to the speed of the brushless DC motor; 3) According to the table of the speed of the brushless DC motor, Combined with the linear interpolation algorithm, the real-time update of the back-EMF zero-crossing detection advance time Ta is performed in real time.

Further, the time Ts0 corresponding to the half sector is subtracted from the back-EMF zero-crossing detection advance time Ta to obtain the back-EMF zero-crossing detection time gap start time. As shown in Figure 4, the time between the start of the back-EMF zero-crossing detection time gap and the detection of the back-EMF zero-crossing point can be defined as the back-EMF zero-crossing detection time gap Tslot, and no back-EMF is performed before entering this time gap Zero-crossing detection. After entering this time gap, when the back-EMF zero-crossing detection advance time Ta is started, the back-EMF is sampled for multiple consecutive single-channel ADs and compared with a reference voltage to determine whether the back-EMF is zero-crossing.

According to another embodiment of the present application, obtaining the back-EMF zero-crossing detection time gap of the brushless DC motor includes: obtaining the time corresponding to the lower half of the current speed of the brushless DC motor, the back-EMF zero-crossing detection advance time, and Freewheeling time interval; Obtain the difference between the time corresponding to half a sector and the back-EMF zero-crossing detection advance time, and place the difference in the free-wheeling time interval to obtain the back-EMF zero-crossing detection time gap.

That is, in the embodiment of the present application, in addition to obtaining the back-EMF zero-crossing detection time gap Tslot according to the time Ts0 corresponding to the half-sector and the back-EMF zero-crossing detection advance time Ta, it can also correspond to the half-sector. The time Ts0 of the back-EMF zero-crossing detection advance time Ta and the freewheeling time interval are used to obtain the back-EMF zero-crossing detection time gap Tslot.

According to an embodiment of the present application, obtaining the freewheeling time interval of the brushless DC motor includes: obtaining the freewheeling time interval according to the highest operating speed of the brushless DC motor; or obtaining the freewheeling time interval by looking up a table according to the current speed; Alternatively, the freewheeling time interval is obtained through a look-up table and a linear interpolation algorithm according to the current rotation speed.

Specifically, the time Ts0 corresponding to the lower half of the current speed of the brushless DC motor and the back-EMF zero-crossing detection advance time Ta can be obtained in the foregoing manner, and then the time Ts0 corresponding to the half-sector is subtracted from the back-EMF time. Zero detection advance time Ta to obtain commutation freewheeling time Tfw, that is, Tfw = Ts0-Ta, and the commutation freewheeling time Tfw needs to satisfy Tfw (min) ≦ Tfw ≦ Tfw (max), ie commutation freewheeling time Tfw needs to be within the freewheeling time interval [Tfw (min), Tfw (max)].

Among them, Tfw (min) is the minimum threshold of commutation freewheeling time, and Tfw (max) is the maximum threshold of commutation freewheeling time, which can be determined by the following three methods: 1) The minimum threshold of commutation freewheeling time, Tfw (min) and commutation freewheeling time maximum threshold Tfw (max) is set to a fixed value, and the fixed value can be configured according to the maximum operating speed of the brushless DC motor; 2) According to the speed of the brushless DC motor, through the look-up table The real-time update of the minimum threshold value Tfw (min) of commutation freewheeling time and the maximum threshold value Tfw (max) of commutation freewheeling time are performed in real time; 3) According to the speed of the brushless DC motor, by looking up the table and combining the linear interpolation algorithm, The minimum commutation freewheeling time threshold Tfw (min) and the maximum commutation freewheeling time threshold Tfw (max) are updated in real time.

Further, as shown in FIG. 5, the time when the commutation freewheeling time Tfw ends is the start time of the back-EMF zero-crossing detection time gap, and the time from the start of the back-EMF zero-crossing detection time gap to the detection of back-EMF The time between zeros is defined as the back-EMF zero-crossing detection time gap Tslot. Back-EMF zero-crossing detection is not performed before entering the back-EMF zero-crossing detection time gap Tslot. After entering the back-EMF zero-crossing detection time gap Tslot, the back-EMF is detected. Single-channel AD sampling is performed multiple times in succession and compared with a reference voltage to determine whether the back EMF crosses zero.

The following describes in detail how to combine the back-EMF zero-crossing detection time gap in the PWM control cycle with a single channel of the ADC module to continuously sample the back-EMF of the brushless DC motor multiple times during the PWM control cycle, and during the sampling process, Determine whether the back EMF crosses zero based on the last sampling result.

According to an embodiment of the present application, if the back-EMF zero-crossing detection time gap is entered, the back-EMF of the brushless DC motor is continuously sampled multiple times, and whether the back-EMF is zero-crossing is detected, including: when the back-EMF zero-crossing detection is entered. During the time gap, configure a single channel of the ADC module as the ADC channel corresponding to the current floating phase terminal voltage and trigger the single channel of the ADC module to sample the back-EMF of the brushless DC motor for the i-th sample, where i is greater than or equal to 1 After the i-th sampling is completed, the i-th sampling result is obtained, and the single channel of the ADC module is triggered to perform the i + 1th sampling of the back electromotive force of the brushless DC motor, and the i + 1-th sampling In the process, it is judged whether the back EMF crosses zero according to the i-th sampling result and the reference voltage; if the back EMF crosses zero, it exits the back EMF zero cross detection stage.

Specifically, referring to FIG. 6a to FIG. 6b, in the process of controlling a brushless DC motor by using a PWM control signal, a PWM control cycle is started and a first preset time is delayed (the length of time is configured by a software program) , Such as 4us) trigger the sampling of the bus voltage AD (because the reference voltage for back-EMF zero-crossing detection is different during the high and low levels of the PWM control signal, so when the back-EMF is performed only during the low-level period of the PWM control signal (There is no need to AD sample the bus voltage during zero crossing detection). The AD sampling of the bus voltage after the first preset time is set to avoid the inaccurate sampling of the bus voltage caused by the influence of the switching of the power switch tube. In the first preset time, the duty cycle of the PWM control signal can be compared and judged. If the duty cycle is less than the second preset duty cycle, the conventional back-EMF sampling method is used to determine whether the back-EMF crosses zero, such as After the sampling of the bus voltage AD is completed, it enters the back-EMF zero-crossing detection stage. At this time, a single channel of the ADC module is used to sample the floating phase terminal voltage once, and the sampling result is compared with the reference voltage to determine whether the back-EMF has passed. Zero; if the duty cycle is greater than the first preset duty cycle, after the sampling of the bus voltage AD is completed, it is judged whether to enter the back-EMF zero-crossing detection time gap. If so, the single channel of the ADC module is used for brushless DC. The back-EMF of the motor is sampled multiple times in succession, and during the sampling process, it is judged whether the back-EMF crosses zero according to the last sampling result.

Specifically, referring to FIG. 6a to FIG. 6b, an AD interrupt is automatically generated after the sampling of the bus voltage AD is completed (about 1us). After entering the AD interrupt, the AD sampling result of the bus voltage is read, and the ADC module ’s The single-channel configuration is the ADC channel corresponding to the current floating phase terminal voltage, and it is prepared for subsequent single-channel back-EMF AD sampling. Then, it is divided into two cases according to the front-back relationship between the start time of the back-EMF zero-crossing detection time gap and the occurrence of AD interruption.

In the first case, as shown in FIG. 6a, after entering the AD interruption, the back-EMF zero-crossing detection time gap has been entered (the corresponding entry into the back-EMF zero-crossing detection phase flag has been set), then continuous in the AD interrupt Multiple single-channel back-EMF AD sampling. The specific sampling process is: first trigger the single channel of the ADC module to sample the back-EMF of the brushless DC motor for the first time, and after the first sampling is completed, read the first sampling result, and simultaneously trigger the single channel of the ADC module The back-EMF of the brushless DC motor is sampled a second time, and during the second sampling process, the first sampling result is compared with the reference voltage to determine whether the back-EMF crosses zero. If the back-EMF crosses zero, exit AD Interrupt, and the back-EMF zero-crossing detection of the current PWM control cycle ends. If the back EMF does not cross zero, then after the second sampling is finished, read the second sampling result and trigger the single channel of the ADC module to sample the back EMF of the brushless DC motor for the third time, and at the third time During the sampling process, it is judged whether the back-EMF crosses zero according to the second sampling result and the bus voltage. If the back-EMF crosses zero, the AD interrupt is exited; if the back-EMF does not cross zero, then after the third sampling is finished, read the first Three sampling results, and trigger the single channel of the ADC module to perform the fourth sampling of the back electromotive force of the brushless DC motor, ... After the i-th sampling is completed, the i-th sampling result is obtained, and the single-channel of the ADC module is triggered at the same time. Perform the i + 1th sampling of the back EMF of the brushless DC motor, and determine whether the back EMF crosses zero based on the i-th sampling result and the reference voltage during the i + 1th sampling process, until it is determined that the back EMF is zero crossing Either the number of samples is greater than or equal to the preset number N or the current PWM control cycle ends, and the AD interrupt is exited.

In the above embodiment, the i-th sampling result is obtained when the i-th sampling is completed, and the i + 1th back-EMF sampling is triggered at the same time. In this way, while using the i-th sampling result to make a back-EMF zero-crossing judgment, the The sampling and conversion of i + 1 times back-EMF is also performed automatically, which is beneficial to collect as much back-EMF as possible during the PWM control cycle. This continuous multiple single-channel back-EMF AD sampling can be reversed in each single channel. The back-EMF zero-crossing judgment is performed when the potential AD sampling is completed, so that the back-EMF zero-crossing can be detected in time, so that the commutation is more accurate, so that the brushless DC motor can run stably at extremely high speed without the need for an additional comparator Can reduce costs.

It should be noted that the preset number of times in the above embodiment is related to the current PWM control period, and N represents the maximum number of times that the back-EMF AD sampling is performed before the end of the current PWM control period.

In the second case, as shown in Figure 6b, after entering the AD interrupt, the back-EMF zero-crossing detection time interval has not yet been entered (the corresponding entry of the back-EMF zero-crossing detection phase flag is not set), then the AD interrupt is exited. The potential zero-crossing detection time interval automatically enters the back-EMF zero-crossing detection timing interrupt TF, and is set in the back-EMF zero-crossing detection timing interrupt TF first to enter the back-EMF zero-crossing detection phase flag, and then performs multiple consecutive single orders Channel back-EMF AD sampling. For the specific sampling process, please refer to the above, which will not be described in detail here.

In order to make those skilled in the art understand this application more clearly, the method of detecting the back-EMF zero-crossing of the brushless DC motor will be further described below with reference to specific examples of this application.

Specifically, as shown in FIG. 7a, the back-EMF zero-crossing detection method of the brushless DC motor may include the following steps:

S501. After entering the AD interrupt, it is judged whether the back-EMF zero-crossing detection time gap is entered. If it is, that is, case one shown in FIG. 6a, step S502 is performed; if not, the AD interrupt is exited.

S502. Trigger single-channel back-EMF AD sampling.

S503: Determine whether the current back-EMF AD sampling ends. If yes, go to step S504; if no, go to step S503.

S504. Read the back-EMF AD sampling result.

S505. Determine whether the back-EMF crosses zero according to the back-EMF AD sampling result. If yes, go to step S507; if no, go to step S506.

S506: Determine whether the current PWM control period ends. If yes, exit the AD interrupt; if not, return to step S502.

S507. Exit the AD sampling and process the back-EMF zero-crossing time.

S508. The zero-crossing detection success flag is set, and the flag bit entering the back-EMF zero-crossing detection phase is cleared.

S509. Set a delayed commutation interrupt TP.

Further, after detecting the back-EMF zero crossing, a delayed commutation interrupt TP is entered to control the brushless DC motor for commutation. As shown in FIG. 7b, the specific method may include the following steps:

S601. Determine whether the zero-crossing detection success flag is set. If yes, execute step S602; if no, exit the delayed commutation interrupt TP.

S602. Control the brushless DC motor for commutation operation.

S603. Update the phase.

S604. Clear the zero-crossing detection success flag.

S605. Set the timing of the back-EMF zero-crossing detection to interrupt TF.

As shown in Figure 7c, after entering the AD interrupt, the back-EMF zero-crossing detection time gap has not yet been entered, as shown in Figure 2b. Once the back-EMF zero-crossing detection time gap is entered, the back-EMF zero-crossing detection timing is automatically entered. Interrupting the TF, the back-EMF zero-crossing detection method may include the following steps:

S701. Set a flag bit for entering the back-EMF zero-crossing detection stage.

S702. Stop the back-EMF zero-crossing detection timing interrupt TF.

S703: Determine whether it is in the current PWM control cycle. If yes, execute step S704; if not, exit the back-EMF zero-crossing detection timing interrupt TF.

S704: Trigger single-channel back-EMF AD sampling.

S705: Determine whether the current back-EMF AD sampling ends. If yes, go to step S706; if no, go to step S705.

S706. Read the back-EMF AD sampling result.

S707. Determine whether the back-EMF crosses zero according to the sampling result of the back-EMF AD. If yes, step S709 is performed. If not, step S708 is performed.

S708: Determine whether the current PWM control period ends. If yes, exit the back-EMF zero-crossing detection timing interrupt TF; if not, return to step S704.

S709: Exit AD sampling and process the back-EMF zero-crossing time.

S710: Set the zero-crossing detection success flag bit, and clear the back-EMF zero-crossing detection flag bit when entering the back-EMF zero-crossing detection stage.

S711. Set the delayed commutation interrupt TP.

Therefore, in each PWM control cycle, the back-EMF zero-crossing detection time gap and the back-EMF zero-crossing can be determined based on the inverse relationship between the start time of the back-EMF zero-crossing detection time gap and the time when the AD interrupt is generated. Detection, and then according to the judgment result, the back-EMF zero-crossing detection is performed on the brushless DC motor through the different methods described above, so as to achieve the purpose of back-EMF zero-crossing determination within the time interval of the back-EMF zero-crossing detection.

FIG. 8 is a schematic diagram of a back-EMF zero-crossing detection of a brushless DC motor according to an embodiment of the present application. As shown in FIG. 8, during an actual operation of the brushless DC motor, an advance time of the back-EMF zero-crossing detection may be calculated. In order to obtain the back-EMF zero-crossing detection time gap Tslot, the back-EMF zero-crossing detection in the back-EMF zero-crossing detection time gap Tslot after the commutation of the brushless DC motor performs a single-channel AD sampling of the back-EMF multiple times in a row, that is, every time During the PWM period, if the back-EMF zero-crossing detection time gap Tslot is not entered, no back-EMF sampling is performed. Once the back-EMF zero-crossing detection time gap Tslot is entered, continuous back-EMF sampling is performed. Therefore, not only the back-EMF zero-crossing point can be detected in a timely and accurate manner, the motor can be stably operated at a very high speed, but also the CPU usage can be reduced. At the same time, no additional comparator is needed, which can reduce costs.

In summary, according to the back-EMF zero-crossing detection method of the brushless DC motor of the embodiment of the present application, the back-EMF zero-crossing detection time gap of the brushless DC motor is obtained, and the back-EMF zero-crossing is detected and confirmed. The time gap is detected, and the back-EMF of the brushless DC motor is continuously sampled multiple times, and the back-EMF is zero-crossed according to the sampling result. Therefore, not only the back-EMF zero-crossing point can be detected in a timely and accurate manner, and the motor can be stably operated at a very high speed, but also without an additional comparator, which can reduce costs.

In addition, the embodiment of the present application also proposes a non-transitory computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above-mentioned method for detecting a back-EMF zero-crossing of a brushless DC motor is implemented.

According to the non-transitory computer-readable storage medium of the embodiment of the present application, by performing the above-mentioned method of detecting the back-EMF zero-crossing of the brushless DC motor, the back-EMF zero-crossing point can be detected in a timely and accurate manner, and the stable operation of the motor at the pole can be ensured. High speed and no need for additional comparators can reduce costs.

FIG. 9 is a schematic block diagram of a back-EMF zero-crossing detection device of a brushless DC motor according to an embodiment of the present application. As shown in FIG. 9, the back-EMF zero-crossing detection device of the brushless DC motor according to the embodiment of the present application may include an obtaining unit 100, a confirmation unit 200, and a sampling unit 300.

The obtaining unit 100 is configured to obtain a back-EMF zero-crossing detection time gap of the brushless DC motor; the confirming unit 200 is configured to detect and confirm entering the back-EMF zero-crossing detection time gap; the sampling unit 300 is configured to The confirmation result of the confirmation unit 200 samples the back-EMF of the brushless DC motor for multiple consecutive times, and performs zero-crossing detection on the back-EMF according to the sampling result.

According to an embodiment of the present application, the obtaining unit 100 is specifically configured to obtain the time corresponding to the lower half of the current rotation speed of the brushless DC motor, and obtain the back-EMF zero-crossing detection advance time of the brushless DC motor, and calculate the half time. The difference between the time corresponding to each sector and the back-EMF zero-crossing detection advance time, and the back-EMF zero-crossing detection time gap is obtained according to the difference.

According to an embodiment of the present application, the obtaining unit 100 is specifically configured to obtain the back-EMF zero-crossing detection advance time according to the highest operating speed of the brushless DC motor; or obtain the back-EMF zero-crossing detection advance time according to the current speed through a look-up table; Or, based on the current rotation speed, a look-up table and a linear interpolation algorithm are used to obtain the back-EMF zero-crossing detection advance time.

According to an embodiment of the present application, the obtaining unit 100 is specifically configured to obtain the time corresponding to the lower half of the current rotation speed of the brushless DC motor, the back-EMF zero-crossing detection advance time and the freewheeling time interval, and obtain a half fan The difference between the time corresponding to the zone and the back-EMF zero-crossing detection advance time, and the difference is in the freewheeling time interval to obtain the back-EMF zero-crossing detection time gap.

According to an embodiment of the present application, the obtaining unit 100 is configured to obtain a freewheeling time interval according to the highest operating speed of the brushless DC motor; or to obtain a freewheeling time interval through a look-up table according to the current speed; or Table and linear interpolation algorithm to obtain freewheeling time interval.

According to an embodiment of the present application, the obtaining unit 100 obtains the number of sampling times of the back-EMF zero-crossing interval according to the current rotation speed, and obtains the number of times of the back-EMF zero-crossing interval according to the previous sampling times; Time Gets the time corresponding to the half sector at the current speed.

According to an embodiment of the present application, the time corresponding to the lower half of the current rotational speed is obtained by the following formula:

Among them, Ts0 is the time corresponding to the half sector of the current rotation speed, Tzci is the i-th back-EMF zero-crossing interval time, N is the number of samples, and N is an integer greater than or equal to 1.

It should be noted that, for details not disclosed in the back-EMF zero-crossing detection device of the brushless DC motor of the embodiment of the present application, please refer to details disclosed in the back-EMF zero-crossing detection method of the brushless DC motor of the embodiment of the present application. , Specifically not detailed here.

In addition, an embodiment of the present application also provides a control system for a brushless DC motor, which includes the above-mentioned back-EMF zero-crossing detection device of the brushless DC motor.

In addition, an embodiment of the present application further provides a vacuum cleaner including the above-mentioned control system of the brushless DC motor.

It should be understood that each part of the application may be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods may be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it may be implemented using any one or a combination of the following techniques known in the art: Discrete logic circuits, application specific integrated circuits with suitable combinational logic gate circuits, programmable gate arrays (PGA), field programmable gate arrays (FPGA), etc.

In addition, in the description of this application, the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "Left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial" The azimuth or position relationship indicated by "", "circumferential", etc. is based on the azimuth or position relationship shown in the drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific The orientation and construction and operation in a particular orientation cannot be understood as a limitation on this application.

In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "plurality" is at least two, for example, two, three, etc., unless it is specifically and specifically defined otherwise.

In this application, the terms "installation," "connected," "connected," and "fixed" should be understood broadly unless otherwise specified and limited, for example, they may be fixed connections or removable connections Or integrated; it can be mechanical or electrical; it can be directly connected or indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction between two elements, unless otherwise specified The limit. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

In this application, unless explicitly stated and limited otherwise, the first feature "on" or "down" of the second feature may be the first and second features in direct contact, or the first and second features indirectly through an intermediate medium. contact. Moreover, the first feature is "above", "above", and "above" the second feature. The first feature is directly above or obliquely above the second feature, or it only indicates that the first feature is higher in level than the second feature. The first feature is “below”, “below”, and “below” of the second feature. The first feature may be directly below or obliquely below the second feature, or it may simply indicate that the first feature is less horizontal than the second feature.

In the description of this specification, the description with reference to the terms “one embodiment”, “some embodiments”, “examples”, “specific examples”, or “some examples” and the like means specific features described in conjunction with the embodiments or examples , Structure, materials, or features are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In addition, without any contradiction, those skilled in the art may combine and combine different embodiments or examples and features of the different embodiments or examples described in this specification.

Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations on the present application. Those skilled in the art can interpret the above within the scope of the present application. Embodiments are subject to change, modification, substitution, and modification.

Claims

A method for detecting a back-EMF zero-crossing of a brushless DC motor, which comprises the following steps:

Obtaining a back-EMF zero-crossing detection time gap of the brushless DC motor;

Detecting and confirming entering the back-EMF zero-crossing detection time gap, sampling the back-EMF of the brushless DC motor, and the sampling is configured to be continuously sampled multiple times;

Back-EMF zero-crossing detection is performed, and the back-EMF zero-crossing detection is configured to perform zero-crossing detection on the back-EMF according to a sampling result.
The method for detecting a back-EMF zero-crossing of a brushless DC motor according to claim 1, wherein the obtaining the back-EMF zero-crossing detection time gap of the brushless DC motor is configured as:

Acquiring the time corresponding to the half sector of the current speed of the brushless DC motor;

Obtaining a back-EMF zero-crossing detection advance time of the brushless DC motor;

Calculating a difference between the time corresponding to the half sector and the advance time of the back-EMF zero-crossing detection;

Acquiring the back-EMF zero-crossing detection time gap, and acquiring the back-EMF zero-crossing detection time gap is configured to obtain the back-EMF zero-crossing detection time gap according to the difference.
The back-EMF zero-crossing detection method of the brushless DC motor according to claim 2, wherein the obtaining the back-EMF zero-crossing detection advance time of the brushless DC motor is configured as:

Obtaining the back-EMF zero-crossing detection advance time according to the highest operating speed of the brushless DC motor; or,

Obtaining the back-EMF zero-crossing detection advance time according to the current rotation speed through a look-up table; or,

Obtain the back-EMF zero-crossing detection advance time according to the current rotation speed through a look-up table and a linear interpolation algorithm.
The method for detecting a back-EMF zero-crossing of a brushless DC motor according to claim 1, wherein the obtaining the back-EMF zero-crossing detection time gap of the brushless DC motor is configured as:

Acquiring the time corresponding to the lower half of the current rotation speed of the brushless DC motor, the advance time of the back-EMF zero-crossing detection, and the freewheeling time interval;

Acquiring a difference between a time corresponding to the half sector and the advance time of the back-EMF zero-crossing detection;

Acquiring the back-EMF zero-crossing detection time gap, and acquiring the back-EMF zero-crossing detection time gap is configured to control the difference to be in the freewheeling time interval to obtain the back-EMF zero-crossing detection time gap .
The method for detecting a back-EMF zero-crossing of a brushless DC motor according to claim 4, wherein the obtaining a freewheeling time interval of the brushless DC motor is configured as:

Acquiring the freewheeling time interval according to the highest operating speed of the brushless DC motor; or

Obtaining the freewheeling time interval by looking up a table according to the current rotation speed; or

The freewheeling time interval is obtained according to the current rotation speed through a look-up table and a linear interpolation algorithm.
The method for detecting a back-EMF zero-crossing of a brushless DC motor according to claim 2 or 4, wherein the obtaining a time corresponding to a half sector of a current speed of the brushless DC motor is configured as:

Obtaining the number of sampling times of the back-EMF zero-crossing interval according to the current rotation speed, and obtaining the back-EMF zero-crossing interval time of the foregoing sampling times;

Acquiring the time corresponding to the lower half of the current rotational speed, and acquiring the time corresponding to the second half of the current rotational speed is configured to acquire the current rotational speed according to the number of back-sampling times of the back EMF zero crossing The time corresponding to the second half of the sector.
The method of detecting a back-EMF zero-crossing of a brushless DC motor according to claim 1, wherein the sampling of the back-EMF of the brushless DC motor to perform back-EMF zero-crossing detection is configured as:

Configure a single channel of the ADC module as the ADC channel corresponding to the current floating phase terminal voltage;

Sampling the back-EMF of the brushless DC motor, and the sampling is configured to trigger a single-channel sampling of the ADC module;

After the sampling is completed, the current sampling result is obtained, and a single channel of the ADC module is triggered to perform the next sampling of the back-EMF of the brushless DC motor;

Performing back-EMF zero-crossing detection, which is configured to perform zero-crossing detection on the back-EMF according to the current sampling result and a reference voltage during the next sampling process;

Detecting and confirming the back-EMF zero-crossing, and exiting the back-EMF zero-crossing detection phase.
The method of detecting a back-EMF zero-crossing of a brushless DC motor according to claim 2, further comprising:

Detect and confirm the difference between the time from the last commutation time to the current time exceeding the half sector corresponding to the back-EMF zero-crossing detection advance time, and enter the back-EMF zero-crossing detection time gap.
The method for detecting a back-EMF zero-crossing of a brushless DC motor according to any one of claims 1 to 8, wherein the highest electric speed of the brushless DC motor is not less than 80,000 r / min.
A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that when the program is executed by a processor, the back electromotive force of the brushless DC motor according to any one of claims 1-9 is realized Zero crossing detection method.
A back-EMF zero-crossing detection device for a brushless DC motor is characterized in that it includes:

An obtaining unit, configured to obtain a back-EMF zero-crossing detection time gap of the brushless DC motor;

A confirming unit, configured to detect and confirm entering the back-EMF zero-crossing detection time gap;

A sampling unit configured to sample the back-EMF of the brushless DC motor, wherein the sampling is configured to perform multiple consecutive samplings to perform back-EMF zero-crossing detection, and the back-EMF zero-crossing detection is configured to Back-EMF performs zero-crossing detection.
The back-EMF zero-crossing detection device of a brushless DC motor according to claim 11, wherein the obtaining unit is specifically configured to obtain a time corresponding to a half sector of a current speed of the brushless DC motor, And obtaining a back-EMF zero-crossing detection advance time of the brushless DC motor, and calculating a difference between a time corresponding to the half sector and the back-EMF zero-crossing detection advance time, to obtain the back-EMF time The zero detection time gap, the obtaining the back-EMF zero-crossing detection time gap is configured to obtain the back-EMF zero-crossing detection time gap according to the difference.
The back-EMF zero-crossing detection device of a brushless DC motor according to claim 12, wherein the obtaining unit is specifically configured to obtain the back-EMF zero-crossing detection according to the highest operating speed of the brushless DC motor Advance time; or, obtaining the back-EMF zero-crossing detection advance time through a look-up table according to the current speed; or obtaining the back-EMF zero-crossing detection advance time according to the current speed through a table lookup and a linear interpolation algorithm.
The back-EMF zero-crossing detection device of a brushless DC motor according to claim 11, wherein the obtaining unit is specifically configured to obtain a time corresponding to a half sector of a current speed of the brushless DC motor, Back-EMF zero-crossing detection advance time and freewheeling time interval, and the difference between the time corresponding to the half sector and the back-EMF zero-crossing detection advance time, and the back-EMF zero-crossing detection time Gap, the obtaining the back-EMF zero-crossing detection time gap is configured to control the difference to be in the freewheeling time interval to obtain the back-EMF zero-crossing detection time gap.
The back-EMF zero-crossing detection device of a brushless DC motor according to claim 14, wherein the obtaining unit is further configured to obtain the freewheeling time interval according to the highest operating speed of the brushless DC motor. ; Or, obtaining the freewheeling time interval by looking up a table according to the current speed; or obtaining the freewheeling time interval by looking up a table and a linear interpolation algorithm according to the current speed.
The back-EMF zero-crossing detection device for a brushless DC motor according to claim 12 or 14, wherein the obtaining unit is specifically configured to obtain the number of sampling times of the back-EMF zero-crossing interval according to the current rotation speed, and Obtaining the back-EMF zero-crossing interval time of the previous sampling times; acquiring the time corresponding to the lower half of the current rotational speed, and acquiring the time corresponding to the lower half of the current rotational speed is configured to be based on the previous The number of sampling times of the back-EMF zero-crossing interval is used to obtain the time corresponding to the lower half of the current rotation speed.
A control system for a brushless DC motor, which comprises a back-EMF zero-crossing detection device for a brushless DC motor according to any one of claims 11-16.
A vacuum cleaner, comprising a control system of a brushless DC motor according to claim 17.